From: Jan Kara <jack@xxxxxxx> Subject: mm: avoid returning VM_FAULT_RETRY from ->page_mkwrite handlers Some ->page_mkwrite handlers may return VM_FAULT_RETRY as its return code (GFS2 or Lustre can definitely do this). However VM_FAULT_RETRY from ->page_mkwrite is completely unhandled by the mm code and results in locking and writeably mapping the page which definitely is not what the caller wanted. Fix Lustre and block_page_mkwrite_ret() used by other filesystems (notably GFS2) to return VM_FAULT_NOPAGE instead which results in bailing out from the fault code, the CPU then retries the access, and we fault again effectively doing what the handler wanted. Link: http://lkml.kernel.org/r/20170203150729.15863-1-jack@xxxxxxx Signed-off-by: Jan Kara <jack@xxxxxxx> Reported-by: Al Viro <viro@xxxxxxxxxxxxxxxxxx> Reviewed-by: Jinshan Xiong <jinshan.xiong@xxxxxxxxx> Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx> Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> --- drivers/staging/lustre/lustre/llite/llite_mmap.c | 4 +--- include/linux/buffer_head.h | 4 +--- 2 files changed, 2 insertions(+), 6 deletions(-) diff -puN drivers/staging/lustre/lustre/llite/llite_mmap.c~mm-avoid-returning-vm_fault_retry-from-page_mkwrite-handlers drivers/staging/lustre/lustre/llite/llite_mmap.c --- a/drivers/staging/lustre/lustre/llite/llite_mmap.c~mm-avoid-returning-vm_fault_retry-from-page_mkwrite-handlers +++ a/drivers/staging/lustre/lustre/llite/llite_mmap.c @@ -390,15 +390,13 @@ static int ll_page_mkwrite(struct vm_are result = VM_FAULT_LOCKED; break; case -ENODATA: + case -EAGAIN: case -EFAULT: result = VM_FAULT_NOPAGE; break; case -ENOMEM: result = VM_FAULT_OOM; break; - case -EAGAIN: - result = VM_FAULT_RETRY; - break; default: result = VM_FAULT_SIGBUS; break; diff -puN include/linux/buffer_head.h~mm-avoid-returning-vm_fault_retry-from-page_mkwrite-handlers include/linux/buffer_head.h --- a/include/linux/buffer_head.h~mm-avoid-returning-vm_fault_retry-from-page_mkwrite-handlers +++ a/include/linux/buffer_head.h @@ -243,12 +243,10 @@ static inline int block_page_mkwrite_ret { if (err == 0) return VM_FAULT_LOCKED; - if (err == -EFAULT) + if (err == -EFAULT || err == -EAGAIN) return VM_FAULT_NOPAGE; if (err == -ENOMEM) return VM_FAULT_OOM; - if (err == -EAGAIN) - return VM_FAULT_RETRY; /* -ENOSPC, -EDQUOT, -EIO ... */ return VM_FAULT_SIGBUS; } _ -- To unsubscribe from this list: send the line "unsubscribe mm-commits" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
